Current technology lies in a plethora of pipettes such as plastic, glass, serological, Pasteur, transfer pipettes and the like, which are manufactured by various companies, including Becton-Dickinson, Corning, Fisher, Bel-Art, Kimble, Wheaton, and many others.
U.S. Pat. No. 2,930,238 to Kellett discloses a pipette which prevents liquid in the pipette from reaching the user's mouth. In this device a ball is provided which floats upwards on the drawn liquid to seal the mouthpiece.
U.S. Pat. No. 4,461,328 to Kenney discloses a pipette device for multiple pipetting which has a hydrophobic sheet to prevent fluid from traversing too far up the tube. The device can be applied to a manifold for applying a vacuum pressure to pipette tubes through filter paper.
U.S. Pat. No. 4,299,795 to Bates discloses a pipette or sample tube for obtaining a column of liquid at a predetermined height in laboratory applications. Movable valve members such as lead shot are located in the tube between the restriction and the opposite end for cooperating with the restriction and the opposite end for cooperating with the restriction to regain a column of liquid at the level of the valve member and restriction by surface tension effects. Liquid is drawn from the tube by suction to a level substantially above the restriction and when the suction is removed, the liquid is allowed to drain out the end by reason of the imperfect seal formed by the lead shot at the restriction.
U.S. Pat. No. 3,864,979 to Ayres discloses a liquid collection tube such as a blood sedimentation tube which is provided with a barrier plug which will permit air passage but prevents liquid passage beyond the bottom of the barrier plug.
U.S. Pat. No. 2,348,831 to Mathis discloses a safety device for pipettes to prevent liquid from being drawn by suction into the mouth. A safety device 11 is provided for automatically preventing liquid drawn into the tube from coming into contact with the mouth of the user. The device 11 is a member attached to one end of the pipette and provided with a mount piece at the other end. The device is structured so that suction may be created in the pipette and air is permitted to pass but not liquid.
U.S. Pat. No. 2,376,231 to Cohn discloses a pipette of the throw-away type, the pipette being packed at its upper end with a cotton filter to prevent passage of bacteria from the mouth of the user into the liquid in the pipette or vice versa.
U.S. Pat. No. 2,423,173 to Brady et al. discloses a safety pipette adapted to pick up liquid by oral suction comprising a tubular member having a barrier member within an enlarged portion The barrier member is pervious to air when dry and impervious to air and liquid when wet.
U.S. Pat. No. 2,692,503 to Crecelius discloses a pipette for use in laboratory work. The pipette is provided with a constriction near the mouth piece to separate the mouthpiece from the main body of the pipette. The restriction is also to prevent the displacement of a cotton plug which is in place to prevent passage of bacteria into the mouth of the person using the pipette.
U.S. Pat. No. 3,995,496 to Bickford discloses a disposable mouthguard for pipettes to prevent the flow of liquid into the user's mouth. The structure of this device is as shown in the drawings.
U.S. Pat. No. 4,589,421 to Ullman discloses a sampling device comprising a collection tube having a capillary passage. The capillary passage has a collecting and dispensing orifice at one end and a second orifice at the other end. A chamber encloses the second orifice. The device has a small opening to the outside atmosphere which is other than the first orifice, and which also communicates with the capillary tube. Also included are non-compressible means movable with respect to the opening for sealing the opening and forcing air from the chamber through the capillary tube.
All currently available pipettes have the same inherent flaw. The user can mouth pipette with them.
Although common sense dictates against mouth pipetting and the National Institutes of Health (NIH) guidelines, among others, prohibit it, this practice still occurs in most laboratories. The relative inconvenience of obtaining an automatic or manual pipetting device to provide suction for pipettes as well as a lack of common sense always results in some users' disregard for existing regulations This is especially true when the user believes that the liquid to be transferred is innocuous. However, the possibility of mislabeling of bottles and/or misreading of labels is the reason that mouth pipetting is discouraged.
Moreover, accidents happen even in the hands of experienced workers, and in many instances, according to the NIH Chemical Safety Office, liability for these accidents may reside with supervisory personnel. This liability may exist even if the worker disregards specific instructions to the contrary and then an accident occurs.
For these reasons, the availability of a pipette which cannot be used for mouth pipetting removes the possibility of accidents while eliminating the onus of liability.
There are available commercial devices, generally referred to as pipetting devices that are designed to be used with standard pipettes. These devices are attached to sources of vacuum or air. Simpler devices exist which use a syringe concept to create sufficient vacuum to draw liquid up into an attached pipette. However, all of these devices serve to prevent the use of mouth pipetting, as well as to simplify pipetting.
The internal operating mechanisms of these pipetting devices are well known in the art and do not form any part of the invention herein.
Most existing pipette devices are adapted to work with standard pipettes. Generally the section of such pipette devices into which an end of a pipette is inserted is referred to as a "nosepiece". The specific structure of these devices vary between manufacturers, but all function similarly. Some nosepieces contain various sized spaced rings formed along the inner walls of the nosepiece The function of the rings is to frictionally hold the pipette in place within the nosepiece. Some nosepieces do not have such rings, but incorporate the concept of tapering the inner walls of the nosepiece such that at some point the pipette will be frictionally and tightly engaged by the inner wall. Some nosepieces use both concepts simultaneously. Many nosepieces provided by various manufacturers incorporate various filters, usually near the top section of the nosepiece, to prevent pipetted liquid from being drawn into the body of the pipette device. Some nosepieces contain check valve devices to prevent liquid being drawn into the body of the pipette device. U.S. Pat. No. 3,963,061, at FIGS. 3, 4 and 5, and column 3, lines 47 to 63, describes the operation of such a device